I am wondering, can the gravel be changed in an established tank if the bioload is light? I have an Eheim ECCO filter and an Emporer power filter on this tank so i should have enough bacteria colonized. Has anyone ever tried this? I would like to have a substrate that would help show off the fish instead of looking so washed out. Right now i have deep river pebble and it seems pretty drab. This is a 54 gal with 1 angelfish, 2 cory cats, and 3 blue rams. I will be adding more fish in a few weeks. My tank is cycled for months now, i just haven't found the right fish yet.